MSBS-5,56 Radom (short for Modułowy System Broni Strzeleckiej kalibru 5,56 mm - Radom or English: Modular Firearm System 5.56mm Calibre - Radom) is an assault rifle currently under development as a future service rifle of the Polish Army. There are two basic variants currently being developed, based on a common upper receiver: a bullpup version and a standard version with folding, retractable stock. Thanks to a variety of modules, both variants can be easily transformed into a carbine, sniper rifle or squad light machine gun. The rifle will be chambered for standard 5.56x45mm NATO ammunition, but a 7.62x51mm NATO version will also be considered.

Currently the standard issue service rifles of the Polish armed forces are a variety of kbs wz.96 Beryl-based rifles, all of them direct descendants of the kbk AKM (a modernized variant of the AK-47 Kalashnikov), developed since the 1940s. However, that design is considered both outdated by modern standards and impossible to improve further. Because of that, work on a completely new family of assault rifles was started in Poland.

The rifle has been in development since 2007 by the WAT (Military Academy of Technology) in Warsaw in cooperation with the arms manufacturer FB Radom. The weapon is said to be operating on completely distinct internal mechanics. No further information has been disclosed however. The external design was conceived by a separate team (Adam Gawron, Bartosz Stefaniak, Grzegorz Misiołek, Maciej Sajdak) working alongside mechanical engineers.

It is expected to go into serial production at the Radom-based Fabryka Broni and enter service by the end of 2014.

For economical reasons the main advantage of the modular weapon system is the simplified logistics because of the interchangeable parts between weapon types of the same family. Fewer parts need to be stored or if necessary, a soldier can sacrifice for example one standard assault rifle to repair a light machine gun.